Charles b



(No Model.)

0. B. SOHOENMEHL.

TREATMENT OF METAL PLATES PRIOR TO ELEUTROLYSIS. No. 494331. PatentedMar. 28,1893.

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THE Noun 5 PETERS cu. PHo'ro-umm WASNINGTON, 04 c.

UNITED STATES PATENT OFFICE.

CHARLES E. SCI-IOENMEHL, OF WATERBURY, CONNECTICUT, ASSIGNOR OF ONE-HALFTO ALDEN M. YOUNG, OF SAME PLACE.

TREATMENT OF METAL PLATES PRIOR TO ELECTROL YSIS.

SPECIFICATION forming part of Letters Patent No. 494,231, dated March28, 1893.

Application filed April 11, 1892. Serial No. 428,637. (No model.)

To all whom it may concern- Be it known that I, CHARLES E. SOHOEN- MEHL,a citizen of the United States, residing at Waterbury, in the county ofNew Haven and State of Connecticut, have invented cer-. tain new anduseful Improvements in the Treatment of Metal Plates Prior toElectrolysis; and I do hereby declare the following to be a full, clear,and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same.

This invention relates to the electro-deposition of metals, but moreparticularly has it reference to processes of electrolysis whose objectis to remove from copper such impurities and foreign bodies as are foundincorporated therewith, thereby leaving the copper in its pure metallicstate.

My present invention has for its object to provide a preliminarytreatment for. plates for the metal to be electrolyzed, and it consistsin coating or otherwise affixing to that side of each plate which in thepath is to be its cathode side, a conductive substance not attacked ordissolved by the chemical action of the electrolyte, but upon whichcopper may be electrolytically deposited as if upon a metallic surface;and for this purpose I prefer to use carbon or graphite, although I donot confine myself to these specific materials.

In order that such persons as are skilled in the art to which myinvention appertains, may fully understand the same, I will now describeit in detail, reference being had to the accompanying drawings which arehereby made a part of this specification, and in which,

Figure 1, is a longitudinal sectional elevation showing a series ofplates prepared in accordance with my invention and arranged in anelectrolytic bath. Fig.2, shows in edge elevation a plate ready to beinserted into the bath. Fig. 3, shows a plate at the time when theprocess is half completed. Fig. 4, is a similar view after thecompletion of the electrolysis.

The system to which my improvement is best adapted is that in which aseries of plates are hung in an electrolytic bath which I designate by Ain the drawings, without any electrical connection between them exceptthrough the electrolyte itself, which latter is preferably a saturatedsolution of sulphate of copper. The positive pole of the electricgenerator makes contact with the electrolyte at one end of the bath, asshown at the left of Fig. 1, and the negative pole makes contact withthe other end of the electrolyte, as appears at the right of saidfigure. The details of these connections are immaterial in thisapplication, but one form thereof is fully described in a certainapplication for Letters Patent executed by me and filed simultaneouslywith this application, Serial No. 428,638.

The plates to be treated may consist either 6 5 of cast or rolledcopper, though the rolled metal is to be preferred on account of itssuperior homogeneity. The difference between cast and rolled copper,however, is one of de-- gree only, and the process is the same withreference to plates made in either way. Such plates are of any sizewhich may be preferred, but a practical plate and one readily handledmight measure from eighten inches to two feet in width by one foot indepth, and from an eighth to a half inch or more in thickness.

Each of the plates B before its introduction into the bath I coat uponone side with a layer C of some electrically conductive, non-metallicsubstance which is insoluble in the electrolyte. For this purpose Iprefer carbon or graphite, and I do not limit myself to any specific wayof applying it, though I prefer to form it into a paint paste or cementby the addition thereto of some viscous or adhesive vehicle. The platesafter being thus treated I arrange in a row or line in the bath, withthe layers of applied material toward the anode pole of the generator,that is, to-

ward the left of Fig. 1, all the uncoated sides 0 The 5 The progress ofthis process 4, whereof Fig. 2 shows the plate with its anode sideintact, as when placed in the bath; Fig. 3, shows the plate with itsanode side half dissolved and a substantially equal amount of copperdeposited upon its cathode side; and Fig. 4 shows the plate as havingitsanode side entirely dissolved and with a deposit upon its cathode sideequal to the original thickness of the plate. By this it will be seenthat during the continuance of the operation of the process each of theplates is losing on one side and gaining at a substantially equal rateupon the other side.

In processes heretofore used and operating upon this principle it isnecessary to leave the plates in circuit untilall the copper of all theplates has been dissolved and re-deposited; and as certain of the platesare apt tov dissolve faster than others, a considerable amount of copperwill be twice dissolved and re-deposited and thisis attended witha wasteof time and current. It is also difficult to tell when the wholequantity of copper has been electrolyzed, but by my process of coatingthe plates with the insoluble layer heretofore referred to, this is doneaway with and certain important advantages are gained. First, other whenthe whole anode side has been electrolyzed and a substantially equalquantity of metal has been deposited upon the carbon surface (compareFigs. 2 and 4) electrolysis ceases as to that plate, and second, theappearance on the anode side of the plate of the layer of carbonindicates that thatplate is finish ed because ofits contrast in colorand it may then be removed from the bath, the remaining plates beingleft until completed. This conduces, as will readily be seen, both toeconomy in the use of the current and to certainty as to the purity ofthe metal deposited. The attached carbon is not in any way detrimentalto the copper when the latter is melted preparatory to working it. Ofcourse it is understood that in the course of this process thedissolution of the copper sets free the precious metals combinedtherewith, as well as any foreign substances, and these descend to thebottom of the bath and there remain as a sediment to be removed fromtime to time, and treated as required.

As heretofore stated, I do not wish to be limited in this invention toany special substance, nor to any specific method or means for applyingit so long as the coatingmaterial is insoluble in the electrolyte and iscapable of taking on metal by electro-deposition. For instance, a sheetof Water-proof fabric coated with carbon or graphite might be cementedor otherwise applied to the cathode side of the plate.

I claim 1. As an improvement in apparatus for purifying metals byelectrolysis, the combination with a containing vessel having positiveand negative electrodes arranged therein, of a series of plates of thecrude metal to be operated upon disposed between the electrodes, eachplate having one face provided with a coating or lay er of material,electrically conductive, but insoluble in the electrolyte.

2. As an improvement in apparatus for purifying metals by electrolysis,the combination with a containing vessel having positive and negativeelectrodes arranged therein, of a series ofplates of the crude metal tobe operated upon disposed between the electrodes, each plate having theface thereof which is opposed to the anode coated with a layer ofnon-metallic material, electrically conductive and insoluble in theelectrolyte, substantially as described.

3. As an improvement in apparatus for purifying metals by electrolysis,the combination with a containing vessel having positive and negativeelectrodes, and an electrolyte arranged therein, of a series of platesof the crude metal to be electrolyzed, arranged between the electrodesin the electrolyte, each of said plates having its cathode face coatedwith a layer of material electrically conductive and insoluble in theelectrolyte and of a color contrasting with the color of the metal uponwhich it is laid, substantially as set forth.

4. The combination with the containing vessel containing the electrolyteand having the electrodes arranged in opposite ends thereof, of a seriesof plates vertically arranged composed of the crude metal to beelectrolyzed, and arranged between the electrodes each plate having itscathode face provided with a layer of carbon or graphite, substantiallyas and for the purpose set forth.

In testimony whereof I affix my signature in presence of two witnesses.

CHARLES E. SCHOENMEHL.

Witnesses:

WILSON H. PIERCE, CoRA R. DEFENDORF.

